1. Technical Field
The present invention relates to a spot color printing color conversion program, a color conversion device and a color conversion method.
2. Related Art
In the related art, if a personal computer instructs the execution of printing to a printer, a color conversion process for converting the values representing the color of each pixel of the image data of an image to be printed into the gradation of ink colors, a halftone process and a rearrangement process are executed and the printer executes printing based on print data generated by these processes. In the color conversion process, image data represented by a RGB color coordinate system is converted into CMYK values by an interpolation operation using a Lookup Table (LUT). However, if a RGB value is not accurately specified in a color management state, the CMYK values converted using the LUT and the CMYK values which accurately representing a desired color on a printing medium will not necessarily coincide with each other. In addition, there are CMYK values which cannot be derived from the interpolation operation using the LUT. To accurately output a desired color, the color conversion using the LUT is not performed, but color conversion is performed by another method with respect to pixels which are to be accurately output in a desired color. For example, generally, like JP-A-2006-287708, color conversion is performed by referring to association information for spot color printing color conversion. In the corresponding information, direct association is performed such that a pixel represented by a specific RGB value of input image data is converted into a desired CMYK value.
In color conversion technology using spot color printing association information, it took a long processing time to distinguish a pixel (hereinafter, referred to as a spot color pixel), which is printed with an ink gradation value specified by a user, from image data of an image to be printed. In detail, if the number of spot colors is Ns, an operation for determining whether the pixel is a spot color pixel with respect to the pixels of image data is performed Ns times without omission, and thus the processing time was long.